Mold and method of making same



New.y 13, 1928.

w.. H. CAMPBELL MOLD AND METHOD oF vMAKING s AME .Filed Sept.. LU.

Patented Nov. 1 3, 1928. 4

' UNIT-ED STATES WALLACE H. CAMPBELL; or' AKRON, o HIo, BER coMrANY, vor NEON-01110,A'CORPORATIQN 0E Oma; A

AssIGNoR 'rolrH'GooDYER TIRE a -MOLD AND M nT'HoD or MAKING SAME.

1 Appncatimi med'septembei 10,: ia27. sr i ai No'. 218,807f f YMy invention relates tomoldsand methods of making them and it has particular relation to a method that' is especially applicable to the production of `vehicle tire molds, and to 5 the product obtained by practising' the method. y

It is customary to construct tire molds entirely of-metal by casting orforgingoperations. Such methods are satisfactory vfor '10 rough work; that is,'for the production of articles having relatively .even surfaces or when" accurac is not' requiredv It is practically impossi le, however, to produce an acc'urate mold having irregular patterns therein, such,

for example, as the tread design ofa vehicle .'tire casing, by either'of these methods,.be

. cause of shrinkage' o f the metal during cool'- t:Dlo overcome this' difficulty, metallic :so-

called fblanks are forged to conform rough- -lgto the desired contour and are'then mac 1 ned to accurate dimensions and configuration. As the machining of the molds' 1s ex-' ceedingly -laborious and time consuming, .it

25. constitutes a large portion of the complete lcost of the mold.

One' ob'ect of my invention is to provide a novel methodo'f making tire molds which obviates the necessity for machining themold. Another object of my invention is tol provide a method of making tire molds which involves the molding of a plastic non-shrinkable substance-to--produce thetread-forming section'of the mold in contra-distinction to A0 the present practice of casting or forging .metal to producea corresponding section.

VA further, object of myinvention is to'provide a. method of makinga tire mold which involves the utilization. of casein or a'casein 40 compound that is molded toproduce thev tread-formingvsection thereof, and applying heatand pressure to harden the section.

For a betterunderstanding of my inven' 45. papying drawings, forming"a part of this f tents AFigi l disposed-'within aan Fig. 3 is a' fragmentary perspective viewof",- a portion of atire mold embodying the features of my invention. In-the practice-of my invention, antiref'or other similar; flexible object l mountedPo'nian 4airbag-g 2 is supportedinamold section''with a` portion of-its: surface, whic h 'includes the tread .design' disposed in` 'spaced relation `to the interior of the mold section.- 'flhe' space;

between the mold section'and the tread surf?.

Aface is -then filled with-.a plastic substance,5 f

and a second 'mold'section 6 issuperimposed i upon the section 3.- lThe section 6 diii'e'rs fromV the .lower surface."l 4-When the. partssection-3 in that it abuts'thetread Vhave been assembled,

just described vand as sho'wn in Fig'l'of .the

together by means of bolts 7 assing throng annular flanges 8 formed on vt e sections, and

'drawing, the inold'. sections are drawn tightl 'l the airbag is inflated to. cause'the inner sur' I face of theplastic material' to assume the contour of 'the tread surface-in intaglio. :The

entire .mold is then inserted *within* anx oven plastic substance 5,.

9 and heated to dry andharden the-'formerly 1 The -present invention part predicated upon myfdiscovery, that -c'asein and com-' y pounds 'containing casein are especially 'ap- .The `substancecommercially knownv as -gala- Sr plic'abl'e for use in forming the tread-form-- o mg surface of the mold, as above described.

lith,'which. is'.'casein rendered insoluble .by

acids' and .then treated with formaldehyde,l

is believed to-be the-preferred form of asein.

to employ. Pure casein and "galalith may both'be obtained commercially in4 powderedv form and are readily 'united with a sucientamount of liquid to render them plastic for When the mold? removed'froni the oven,

thel tread-formin "surfa'c'e .10 thereof is prace -tically'perfectintontour, and, therefore, re# l l l that the. casein or the ca'sem compound emqnires no machining, by reason of the fact' ploy'eddo'es notsl1`rink perceptibly' as. it 1ihardens to'solidform. This surface is also non-inflammable, is"v asihard' as stone and does 'not soften or melt at temperatures far above' that employed yin the vulcanization of tires'.

Although I have illustratedonly one/form' which my invention may assum and ha,v e 

